Colorblindness, formally referred to as color vision deficiency, affects about 8% of men and 0.8% of women globally. Colorblindness causes those affected to have a difficult time discriminating certain color combinations and color differences. Colors are perceived by viewers through the absorption of photons followed by a signal sent to the brain indicating the color being viewed. Generally, colorblind viewers are deficient in the necessary physical components enabling them to distinguish and detect particular colors. As a result of the loss of color information, many visual objects, such as images and videos, which have high color quality in the eyes of a non-affected viewer, cannot typically be fully appreciated by those with colorblindness.
Several research works have been dedicated to helping such users better perceive visual objects with color combinations and color differences that are difficult for those with colorblindness to detect. One approach is to recolor the objects, that is, adopt a mapping function to change the colors of the original images, such that the colors that are difficult for the colorblind users to distinguish are mapped to other colors that can be distinguished. However, many recoloring approaches have two major flaws. First, they have huge computational costs. Many methods adopt an optimization process to determine the color mapping function. This introduces large computational costs, and thus they can hardly be applied in real-world applications, especially in real-time video recoloring which typically requires each frame to be processed in less than 1/24 of a second. Second, many recoloring approaches have a color inconsistency problem. For example, the color mapping function may depend on the distribution of colors, i.e., the mapping function will be different for different images. This is not a problem for still images, but it will degrade a user's experience in video recoloring. For example, in two nearby frames, the colors of a particular person's face may be mapped to different colors, and this may confuse the user.